Reverse Actuated Nail Clipper with Mechanical Advantage

ABSTRACT

A device for clipping fingernails and toenails of human beings that differs from other nail clippers by reversing the end of the clipper on which a user presses to perform nail clipping. Instead of the user pressing down on the end opposite the nail clipper&#39;s cutting edges, the current invention allows the user to press down directly above where the clipper cuts the user&#39;s nail. This invention also incorporates a roller on the primary lever that engages with the second lever that the user presses down on, in a manner that continuously increases the cutting force of the clipper as the second lever is pressed further down. These features make the nail clipper easier to use while also giving the user greater control, an easier and more powerful clipping force and greater accuracy, which are the objects of the invention. 
     The invention is an extension of traditional nail clippers in that it adds a second lever assembly that pivots on a hinge located at the end of a common art nail clipper, opposite the end having the cutting edges. The second lever assembly is shaped so that a roller mounted on the free end of the first lever, and attached at its other end close to the cutting edges of the clippers, rolls along the inside back surface of the second lever starting near the underside of the second lever&#39;s thumb pad and continuing to roll towards the hinged end of the second lever as the second lever is pressed down towards the clipper cutting edges to execute clipping a fingernail or toenail. 
     As the user presses down on the second lever the first lever also moves down towards the clipper cutting spring arms forcing the clipper cutting edges to close and clip a nail. The user operates the nail clipper by pressing a thumb pad, which is located at the free end of the second lever, down towards the cutting edges, which close together as the user executes this operation. When the user releases their downward pressure from the thumb pad, the nail clipper&#39;s cutting edges separate again as the two levers free ends move back up away from the clipper&#39;s cutting spring arms.

REFERENCES CITED U.S. Patent Documents

-   U.S. Pat. No. 741,709 October 2003 Petrelli . . . 30/28,30/188 -   U.S. Pat. No. 2,570,025 December 2048 Davis . . . 30/28 -   U.S. Pat. No. 4,176,449 December 2079 Lee, Lee . . . 30/28 -   U.S. Pat. No. 4,640,011 February 2087 Gamble . . . 30/28 -   U.S. Pat. No. 5,226,849 July 2093 Johnson . . . 30/28 -   U.S. Pat. No. 5,392,518 February 2095 Means . . . 30/28 -   U.S. Pat. No. 5,522,136 June 2096 Larisey . . . 30/28 -   U.S. Pat. No. 6,705,014 B2 March 2004 . . . Park 30/28 -   U.S. Pat. No. 6,735,869 B2 May 2004 Lau . . . 30/28 -   U.S. Pat. No. 7,234,238 B2 June 2007 Wong . . . 30/28 -   U.S. Pat. No. 7,530,170 B2 May 2009 Shackelford. 30/28 -   U.S. Pat. No. 8,578,612 B2 October 2013 Doane . . . 30/28, 30/26

BACKGROUND OF THE INVENTION 1. Field of the Invention

The invention relates to a nail clipper for clipping the fingernails or toenails of human beings in a manner that makes it easier to clip tough nails and to control where the cutting edges are positioned prior to clipping and remain positioned during the clipping. The user actuates the invention's clipping operation by applying pressure between the thumb and forefinger directly above and below the clipper's cutting edges, and with their other fingers cradling the underside of the clipper, such that there is no resultant force that might cause the cutting edges to move from the desired position for cutting the user's nail.

2. Description of Related Art

Various nail clippers have been provided that all perform the basic clipping operation. They are primarily comprised of the cutting arm springs joined together at one end and having slightly separated and opposing cutting edges on their other end. Some of these designs are U.S. Pat. No. 5,226,849 and D. 392,419. The current invention employs a modified first lever which is relatively shorter than the first lever in prior art common nail clipper designs, and which first bends upwardly at a more extreme angle than in prior art common nail clipper designs and then curves downwardly before straightening out so that its end is largely parallel to the cutting arm springs of the nail clipper. This first lever is also designed to hold a small roller at its free end so that the roller touches the underside of a second lever and rolls along its underside between the two side walls of the downward U-shaped channel of said second lever. The second lever arm pivots on a hinge that is integrated and attached to both cutting arm springs at the end opposite their cutting edges. The addition of the second lever arm assembly, along with the modified first lever and its integrated roller, together result in the current invention's improved usability and increased cutting force provided by a continuously increasing mechanical advantage and differentiate it from the prior art. U.S. Pat. No. 4,176,449 employs a similar design which envelops an unmodified common nail clipper of prior art in a two part hinged apparatus that includes a second lever arm to press down on the lever of the enveloped common nail clipper of prior art. The device described in U.S. Pat. No. 4,176,449 uses a second lever with a U-shaped cross-section that engages with a first lever but does not include a roller on the first lever that would provide for smoother use, as the current invention provides. This design requires the hinge point for the second lever to be considerably further away from the nail clipper's cutting edges than the ends of a common nail clipper's cutting arms are so that the angle at which the common nail clipper's lever hits the second lever is acute enough to allow it to slide along the second lever as the second lever is rotated towards the clipper's cutting edges during use. This device requires a second clamping bar to be riveted to the end of the common nail clipper to extend the common nail clipper's cutting arms so that the longer second lever can be hinged to the clamping bar at the end farthest from the common nail clipper's cutting edges. This results in a device that is considerably longer than a common nail clipper which violates one of the goals of the current invention. Further, this invention also differs from the current invention in that it is not an integrated part of the nail clipper, which reduces aesthetic beauty and could result in the invention clamp loosening and separating from the nail clipper during use.

Another of these designs is U.S. Pat. No. 8,578,612, by the same inventor as the current invention, which is largely similar to the current invention except for the location of the roller. U.S. Pat. No. 8,578,612 includes a roller on the second lever and a hollow backside to the second lever that allows the first lever to pass through the second lever during use. The problem with this design is the mechanical advantage, and resulting clipper cutting force, is reduced as the roller on the second lever moves forward on the first lever as they are both pressed down during use. This results in an effectively shorter first lever with a lower mechanical advantage at the end of a clipping action versus at the beginning. The current invention allows the user to create more force at the end of a clipping action without increasing the force applied to the first lever, thereby making it easier to complete the clip, or cutting, of the nail. In the current invention the second lever acts as a class 2 lever with the load, or resistance, applied by the roller on the first lever and the roller moving towards the fulcrum during use, which reduces the length of the load arm with no change to the length of the effort arm, thereby increasing the mechanical advantage and the force against the roller mounted on the first lever.

Alternate prior art function using a scissors-like action that closes the cutting edges. Some of these designs are relevant as their goal is similar to the current invention. These designs, covered by U.S. Pat. No. 741,709 and D629,161 S, add a lever arm to the scissors-like design that allows the user to apply pressure close to the location of the cutting edges in a manner similar to the current invention. While this design is similar to the current invention in that they share the goal of allowing the user to apply force close to the cutting action, the scissors-like cutting action is different from the current invention's cutting action.

SUMMARY OF THE INVENTION

Traditional fingernail and toenail clippers require a user to apply pressure to the clipper's levers/handles at the end opposite the cutting edges. The current invention reverses this to allow the user to apply force close to the cutting edges, thereby making the tool more ergonomically correct and easier to use. The current invention takes the traditional nail clipper design and adds a second lever arm assembly that rotates on a pivot point attached to the edge of the cutter arms at the end opposite the cutting edges. The additional lever arm assembly is shaped such that when pushed down by the user it will push down on the roller mounted on the clipper's other lever arm which causes the cutting edges to close together with ever increasing force to clip the nail.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a right side elevational view of the clippers with the second lever unfolded just enough to show the roller mounted to the end of the first lever, and including a nail file inset into the side of the second lever;

FIG. 2 is an isometric view from the top right side of the clipper with the second lever rotated away from the clipper;

FIG. 3 is an isometric view from the top right side of the clipper with the second lever positioned for starting a nail clipping action;

FIG. 4 is an isometric view from the bottom right side of the clipper with the second lever's bottom surface touching the roller on the first lever and ready for starting a nail clipping action;

FIG. 5 is a right side elevational view of the clipper partially unfolded and without a nail file inset into the side of the second lever;

FIG. 6 is a right side elevational view of the clipper without its second lever attached to the clipper;

FIG. 7 is a top view of the clipper without its second lever attached to the clipper;

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings the user presses downward on what has heretofore been referred to as the second lever, 3 in FIGS. 1-5, at the thumb pad, 3 a, located at the end of the free end of the second lever opposite it's fulcrum or hinge pin, 6, and above the cutting edges, la. In one manner of operation the user's thumb will be positioned on the thumb pad of the second lever, 3, while the user's fingers will be underneath the lower cutting arm spring, 1, supporting the nail clipper, and with their index finger closest to the cutting edges, la. The thumb pad moves down towards the cutting edges, la, while the second lever, 3, rotates about its fulcrum or hinge pin, 6, when the user presses their thumb towards their index finger. This downward movement causes the underside back surface of the second lever, 3 b, to press down on the roller, 5, mounted at the free end of the nail clipper's first lever, 2. This causes the first lever, 2, to move down and rotate around its lower end heel, 2 a, which serves as an integrated fulcrum as it engages in the slot of the support and pivot pin, 4, hereafter referred to as the support pin. The support pin, 4, remains fixed while applying upward pressure on the lower cutting arm spring, 1, while the first lever, serving as a second class lever, rotates counter-clockwise, when viewed from the right side of the clipper, which causes the first lever, 2, to press down on the upper cutting arm spring, 1, where the bend or heel, 2 a, in the first lever presses onto the upper cutting arm spring, 1. Together these actions cause the upper and lower cutting arm springs, 1, to flex towards each other thereby closing the gap between the cutting edges, until they meet and cut a fingernail or toenail.

In FIG. 1, the second lever, 3, has a nail file, 7, integrated and attached to each side of the second lever, 3. In the preferred embodiment of the invention the nail files are attached in insets that are slightly recessed so as not to rub or catch against other surfaces or the user's hand when using the nail clippers.

In the preferred embodiment of the invention, the user moves the second lever, 3, towards the clipper cutting arms, 1, the roller, 5, mounted on the first lever, 2, and secured to the first lever with the shaft pin, 2 b, moves along the second lever's underside back surface, 3 b, in a direction from the free end towards the hinged end of the second lever, 3. As the roller moves closer to the hinged end of the second lever, 3, the effective lever effort to load length ratio increases thereby applying more force against the roller, 5, for a constant force applied by the user when executing a nail clipping action. 

1. The invention of a new and improved fingernail and toenail clipper comprised of two cutting arms with cutting edges at one end and joined at the other end where a cylindrical barrel is also attached to serve as hinge joint. At the front end close to the cutting edges, a support and pivot pin penetrates through both cutting arms and extends out the top where it engages a loose actuating lever, the primary actuating lever, which is shaped to seat in a notch in the support and pivot pin allowing it to rotate around the support and pivot pin and to lie in a somewhat flat position on the top cutting arm when closed and to close the cutting edges when in the open position. The primary actuating lever has a sharp upward bend, when in the open position, just back of the support and pivot pin and ending with a roller mounted at the free end of the primary lever. The primary lever and roller assembly end at a point above the cutting arms between two-fifths and two-thirds their overall length measured from the cutting edges. A second lever rotates about a pin running through the lever assembly at its rear end and through the hinge joint at the end of the cutting arms. The second lever assembly includes a horizontally oriented thumb pad at its free end, and includes an downward-facing, U-shaped channel along its length from where it hinges up to or including the portion that comprises the thumb pad. The primary lever and roller are sized in width to fit inside the second lever assembly channel and in length such that the roller rolls along the bottom side of the horizontally-oriented, top wall of the second lever. Together these all comprise a reverse-operated nail clipper equal in length to a common nail clipper of prior art, but easier to operate with greater accuracy and with less force required.
 2. The invention of claim 1 comprising all the features and embodiments described above but to include an integrated nail file on one or both sides of the second lever. 